1. Field of the Invention
The present invention generally relates to a photographic camera system utilizing interchangeable objective lens assemblies one at a time and, more particularly, to an improvement in coordination between the camera body and the interchangeable objective lens assembly then coupled thereto.
2. Description of the Prior Art
In a photographic camera system utilizable with interchangeable objective lens assemblies one at a time, one of the most important coordinations between the camera body and the lens assembly then coupled thereto lies in the manual aperture setting required to be performed at the time of manual exposure control, automatic exposure control under the aperture-priority mode, or the like. As is well known to those skilled in the art, interchangeable lens assemblies generally have a manipulatable aperture adjustment such as an aperture setting ring mounted exteriorly on the lens barrel for the access to a photographer.
On the other hand, there is also known a photographic camera system wherein the aperture adjustment is not provided on an interchangeable lens assembly, but on the body of a photographic camera so that the setting of the aperture adjustment can be transmitted to the lens assembly to control the aperture in such lens assembly. In this camera system, since the available aperture range, i.e., the available range from the maximum settable aperture (the smallest available f-stop number) to the minimum settable aperture (the largest available f-stop number), varies from one interchangeable lens assembly to another, a mechanism comprising a mechanical signaling element, provided in any one of the interchangeable lens assemblies and indicating the aperture range available in the respective lens assembly, and an engagement element provided in the camera body for engagement with the signaling element is employed to inhibit the aperture adjustment in the camera body to set the aperture of a value outside the available aperture range.
In either of the above described camera systems, there are many limitations and/or requirements imposed on the manufacture of the interchangeable lens assemblies such as, for example, a space for accommodating an arrangement necessary to permit the aperture setting ring to rotate, a precise arrangement of both the signaling element and the engagement element, the precise machining of the associated component parts and so on. These limitations and/or requirements often render the camera system as a whole to be complicated and expensive.
Another one of the most important coordinations between the camera body and the lens assembly lies in the transmission of various electric signals therebetween. Numerous techniques and arrangements have hitherto been utilized for transmitting electric signals through terminals between the camera body and the lens assembly. As is well known to those skilled in the art, the utmost care is required to permit the electric signals to be correctly transmitted between the camera body and the lens assembly and, therefore, an improvement has long been desired to avoid any possible inadvertent transmission of one or more of the electric signals from the camera body to the lens assembly or from the lens assembly to the camera body which would result in the erroneous operation of the camera.